Method and apparatus for selective fusing

ABSTRACT

A method and apparatus for selectively fusing a toner image configuration to a support material while not effecting fusing of randomly deposited toner in non-image areas. The fuser utilizes a heat source which creates a sufficient amount of heat in the dense toner image areas on the support material to cause toner to permanently adhere thereto. The unbonded toner in the non-image areas may then be readily removed after fusing to produce a high quality reproduction. The fusing method and apparatus of the invention utilizes a series of diagonally oriented parallel wires to support the support material during fusing to minimize uneven heat conduction from the support material.

I United States Patent [15] 3,648,991 Volkers 51 Mar. 14, 1972 [54]METHOD AND APPARATUS FOR SELECTIVE FUSING Primary Examiner-Charles J.Myhre Attamey-Donald F. Daley, James .I. Ralabate and James P. [72]Inventor: Stewart W. Volkers, Williamson, N.Y. m

[73] Assignee: Xerox Corporation, Rochester, NY.

[57] ABSTRACT [22] Filed: Aug. 19, 1969 l A method and apparatus forselectively fusing a toner image PP 51,403 configuration to a supportmaterial while not efiecting fusing of randomly deposited toner innon-image areas. The fuser [52] U 8 Cl 263/6 E utilizes a heat sourcewhich creates a sufficient amount of heat [5 g 15/20 in the dense tonerimage areas on the support material to [58] Fieid 263/6 6E cause tonerto permanently adhere thereto. The unbonded toner in the nn image areasy then be readily removed after fusing to produce a high qualityreproduction. The fusing [56] References cued method and apparatus ofthe invention utilizes a series of UNITED STATES PATENTS diagonallyoriented parallel wires to support the support material during fusing'tominimize uneven heat conduction 3,409,280 1 1/1968 Spr ngett ..263/6 E fthe Support materiaL 3,448,970 6/1969 Kolibas ...263/6 E X 3,5 l 9,2537/1970 Aser et a]. ..263/6 E 11 Claims, 3 Drawing Figures PAIENTEHMAR 14\912 INVEN O FIG. 3 STEWART w. V TJLII{(ERS 021 A RNEY METHOD ANDAPPARATUS FOR SELECTIVE FUSING BACKGROUND OF THE INVENTION Thisinvention relates in general to fusing a visible image to a supportmaterial and, in particular, to an improved selective fusing method andapparatus.

More specifically, this invention relates to a selective fusing methodand apparatus wherein a heat source selectively fuses developer materiallying in image configuration onto a support material while randomlydeposited toner lying in non-image areas is not bonded thereto. Themethod and apparatus according to the present invention includes animproved platen for supporting the support material during fusingwherein a series of diagonally oriented parallel wires minimize the heatconduction loss between the support material and the support membermaintaining it. The unbonded background toner particles are thereafterremoved by any convenient method to form a high quality reproduction ofan original document or the like.

In the process of xerography, a xerographic surface comprising a layerof photoconductive material on a conductive backing is given a uniformelectric charge on its surface and then is exposed to the subject matterto be reproduced by various projection techniques. This exposuredischarges a plate in accordance with the light intensity reaching itthereby creating a latent electrostatic image on or in the plate.Development of the image is effected by developers which may comprise,in general, a mixture of suitable, pigmented or dyed, resin base powder,hereinafter referred to as toner, which is brought into contact with thesurface by various well-known development techniques. During suchdevelopment of the image, the toner powder is brought into surfacecontact with the photoconductive coating and is held thereelectrostatically in a pattern corresponding to the latent electrostaticimage. Thereafter, the developed xerographic image may be transferred toa support material to which it may be fixed by any suitable means suchas heat fusing.

Several techniques have been employed in the prior art to accomplish theaforementioned fusing of the transferred developed image to the supportmaterial. One well-known method of fusing the toner powder to thesupport material has been by the application of heat to melt theparticles into a bond with the support material. Such a manner of fusingis disclosed in the US. Pat. No. 2,297,691 to Carlson wherein a heatingelement is placed near the surface of the support material bearing adeveloped image whereupon the heat from the heat source will melt theparticles into a bond with the paper. However, the employment of suchheat to fuse the toner image to the support material has presented theproblem of also fusing toner particles deposited in non-image areas tothe support material, which will mar the quality of the reproduction.Generally, upon exposure of a photoconductor surface, a residualelectrostatic charge remains in the nonimage areas of the surface whichduring development will randomly attract toner particles thereto. Suchattracted toner particles in the background areas will transfer with thedeveloped image onto the support material and, when fused into a finalreproduction, will produce undesired bonded toner in non-image areas.The problem of fusing toner in background areas becomes especiallycritical when the reproduction is to be utilized as a master copy formaking subsequent copies, since when background toner is fused to amaster, the subsequent copies made therefrom tend to readily revealbackground development even when the background fused toner is notobservable on the master.

A technique of fusing has been utilized in the prior art to overcome thedeficiencies of fusing toner particles to nonimage areas as occurs inthe basic heat fusing systems. Such an improved fusing system isdisclosed in the US. Pat. No. 3,411,932 to Malone et al. wherein aselective heat fusing technique is employed that effects fusing of onlytoner lying in image areas of the support material. Thereafter, thenonbonded background particles may be readily removed to produce a highquality reproduction of the' original subject matter. However,.such asystem of selective fusing has encountered several problems in. creatinga high quality reproduction. Selective fusing is basedupdn the technicalprincipal that toner is densely. adhering in developed image areaswhereupon a particular heat wavelength radiation level is selected tocause the dense image material to melt into a bonding relationship withthe support materialwithout effecting bonding of the toner adhering innon-image areas. Generally, the background toner materials ,do notdensely affix to the non-image areas of the surface and, therefore, thecooling rate of these particles is sufficienmo prevent their meltinginto a bonding relationship with the support material at certain heatlevels that do cause bonding of image particles.

The selective bonding of image tonerto the exclusion of backgroundparticles is effected because the support material absorbs significantlyless impingingradiation at certain wavelengths than toner adhering inimageand background areas thereof. Accordingly, the energy input perunit area of the support material is less than the adhering tonerparticles and thus a level of energy may be selected which allowsadequate cooling of background toner toprevent-their bond? ing while atthe same time melting the denser particles in image areas into a bondwith the support material.- However, selective fusing requiresanaccurate application of energy to the support surface to achieve thedesired result of not fusing background toner. This accurate applicationfurther requires that the temperature remain uniform on the supportmaterial and not be raised in certain areas to an energy level whichprevents the aforementioned desired cooling of background toner.

However, the support material has heretofore been supported on a flatplaten which during selective fusing creates a variation of heatconduction from the material to the platen to thereby cause the energylevel in certain areas of the support material to -be greater thaninothers wherein the high heat levels can be sufficient to effect theaforementionedundesired bonding of the background toner. Thevariation'of heat conductionwgenerally is created becauseof-*the.differences-.in platen temperature over its surface andthenon-uniformity of contact between the platen and the supportmaterial. Further, since the temperature of the support material is acritical consideration in selective fusing, it becomesimportant tocontrol its temperature priorto fusing. However, the use'of aflatsupport platen also retains heat after fusingwhich preheatssubsequentlyused supportmaterial to an extent to interfere adversely with theselective fusing process.

One solution to the problems presented by a flat platen during selectivefusing would be an attempt'tovobtain uniform conduction of heat from thesupportvmaterial during fusing which is, however,- virtually impossible.Therefore, itbecomes desirable to attempt tothermallyisolate'the supportmaterial from the platen member as much as'possible'to minimize anycontact therebetween and prevent the non-uniform heat conductiondifficulty. By so minimizing heat conduction, thetemperature of thesupport medium may be more efiectively controlled to effect the desiredlevel ofenergyutransfer-between the particles and the supportmaterialforaccurateselective fusing. Also, a minimum contact platenalleviatesthe problem of preheating the support material becauseofthe retention ofenergy in'the platen from previous fusing operations.

SUMMARY OF THE INVENTION It is, therefore, an object of this-inventionto improvethe method and apparatus for fusing a toner imageto a supportmaterial.

Another object of this invention is to improve the method and apparatusfor selectively fusing toner adhering to the image areas of the supportmaterial thereto.

A further object of .this invention is to minimize the contact of theplaten maintainingthe support material during fusing.

Still another object ofthis invention'is to-preventthe preheating of thesupport material before fusing.

These and other objects are obtained in accordance with the presentinvention wherein there is provided a selective fusing method andapparatus that utilizes a minimum contact platen for supporting asupport material during the fusing operation. The improved supportplaten of the present invention includes a grid member which issupported above a concave reflecting platen to prevent variations inheat conduction from the image bearing support material thereto. As thesupport material moves across the grid platen, a minimum of heatconduction is produced between the support material and the platenduring fusing because of the small physical contact existingtherebetween. Such minimum contact not only insures the accurateselective fusing of toner to image areas to the exclusion of non-imageparticles, but further will not preheat the support material to anextent great enough to cause background residual toner to bond to thesupport material during fusing. By producing such accurate environmentalcontrol of the paper during fusing, the unbonded toner in backgroundareas may be readily removed from the support material after fusing ofimage toner to produce a high quality reproduction which can be used forsuch purposes as a master for subsequent copies. Therefore, the presentinvention presents a novel method and apparatus which improves theselective fusing of toner to image areas to the exclusion of tonerrandomly adhering to non-image areas.

DESCRIPTION OF THE DRAWINGS Further objects of the invention togetherwith additional features contributing thereto and advantages accruingtherefrom will be apparent from the following description of oneembodiment of the invention when read in conjunction with theaccompanying drawings wherein:

FIG. 1 is a schematic illustration of a xerographic machine utilizingthe selective fusing system of the present invention.

FIG. 2 is a perspective illustration of the selective fusing system ofthe present invention.

FIG. 3 is a top schematic illustration of the minimum contact platenutilized in the fusing system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there isshown for purposes of illustration a schematic view of a drum typeautomatic xerographic reproducing machine utilizing the presentinvention. The central element of the apparatus is a drum I mounted forrotation and driveable in a conventional direction by motor M. The drum1 comprises an outer surface having a layer of photoconductiveinsulating material such as, vitreous selenium, or other suitablesurface. A uniform electrostatic charge is placed on the photoconductivesurface of the drum by means of a conventional corona charging device 2.The uniformally charged surface on the drum is then moved to an exposuremeans 3 which may be any well-known device which will expose the chargedsurface to copy to be reproduced to thereby form a latent electrostaticimage of the copy on a photoconductor drum surface in a manner wellknown in the art.

Following the formation of a latent electrostatic image of the copy tobe reproduced, the image on the drum will move to a development device 4to bring the electrostatic image into contact with developer material,comprising charged toner, to develop the latent image. After developmentthe visible image moves to a transfer means 9 and is transferred fromthe drum to a sheet of paper or other suitable support material which isbrought into contact with the drum by a conventional support materialfeeding system 5. A second corona charging device 6 applies a charge toa side of the sheet of support material opposite the developed image tofacilitate transfer of the toner powder in image form. The toner imageon the sheet thereupon moves past the selective fusing system accordingto the present invention (to be described in detail later) whichpermanently affixes the toner to the sheet material to form a duplicateof the original copy. A cleaning device 7 contacts the photoreceptorsurface after it moves past the transfer device to remove any residualimage material on the surface prior to a subsequent reproduction cycle.It should be clear that other modes of charging, exposing, developingand transfer may be utilized in connection with the present invention.

Referring now to FIG. 2, there is illustrated an embodiment of theselective fusing device 10 of the present invention. The fusing deviceis positioned to receive the support material after a developed imagehas been transferred thereto. The fusing device comprises a housing 11which includes a shaft 12 rotatably mounted across the entire width ofthe housing at the entrance 13 thereof. The exit end 14 of the housingincludes a similar shaft 15 rotatably mounted by suitable means. Each ofthe shafts l2 and 15 include a roller element adapted to retaintherebetween a series of transport belts and each of the belts extendaround the two rotatable shafts. The transport belts are any suitablematerial to carry and transport a sheet or the like of support materialfrom the transfer device and are driven by suitable motor means (notshown) connected to the shaft 15 to move the belts and transport thesheet support material at a desired speed. The belts are furthermaintained by two roller elements 17 rotatably mounted beneath thenoncontact platen l8 and two roller elements 17a rotatably mounted oneach side of the focusing area l9 to facilitate the belt passing underthe fusing area in a non-interferring manner. Edge guides 20 are mountedat the entrance of the fusing area to contact the two edges of thesupport material as it moves thereby to insure that the support materialpasses in a flat condition through the fusing area.

A rotatable shaft 21 is mounted in brackets at the entrance of thefusing area and includes two edge rollers 22 which contact the edge ofthe support material and positively guide the support material into thefusing area 19. The front of the sheet of support material entering thefusing area is moved therethrough by the rest of the sheet member stillin contact with the conveying belts 16. As the sheet is conveyed throughthe fusing area, the leading edge of the sheet reaches the conveyingbelts 16 at the exit area 14 of the housing which then pulls thetrailing part of the sheet through the fusing area. A pressure roller 23is rotatably mounted at the exit side of the fusing area to receive thesupport material from the fusing area for pressing the sheet materialinto positive contact with the conveying belts and for preventingcurling of the sheet. Two additional edge guides 24 are mounted on eachside of the housing in the fusing area to maintain the sheet of supportmaterial flat during fusing.

The fusing area 19 includes a source of heat energy produced by aconventional means 25 such as, for example, a quartz infrared lampmounted by suitable means above the path of movement of the imagebearing support material. The quartz lamp is connected to a suitablevoltage potential (not shown) to create a desired level of heat forsuitable fusing and the lamp is surrounded by a cylindrical reflector 26having a reflective surface to concentrate the heat therefrom to thesupport material having an image to be fused thereon. The surface of thereflector may be any suitable material which transmits the desired levelof heat to the support sheet and may be, for example, a gold surfacewhich creates a high reflectance for an infrared lamp. The toner imageto be fused lies on the support sheet in direct confrontation to thequartz lamp whereby the heat therefrom is absorbed by the toner in theimage areas. Since the developer in the image areas is relativelydensely packed, the cooling rate therein is not sufficient to preventthe toner from melting into a bond with the support material.

However, toner deposited randomly in the non-image areas is generallymuch less dense than in the image areas and thereby the heat levelcreated by the lamp is insufficient to melt the toner into a bondingrelationship with the sheet, since the cooling rate of non-image toneris great enough to prevent melting thereof. Therefore, the image toneris permanently fused to the sheet of support material while thebackground particles are not bonded which are then in condition to bereadily removed from the support material. After fusing, the sheet isconveyed by suitable means to a removal device 8 where the unbondedbackground toner is removed from the duplicate. The removal device maybe any device capable of removing the background particles such as, forexample, disclosed in the aforementioned US. Pat. No. 3,41 1,932 oralternatively, the unbonded toner may be removed by hand. After theunbonded particles are removed, a permanent high quality duplicate ofthe subject matter to be reproduced is conveyed to a utilization stationwhereupon it may be removed by an operator or other utilization means.

Referring now to FIG. 2 and FIG. 3, the platen 18 supporting the supportmaterial during fusing is illustrated and comprises a grid 27 of thinparallel wires which are diagonally strung between two elongated members28. Any number of wires may be utilized in connection with the presentinvention depending on the degree of support and heat isolation desiredfor the support material. A concave reflecting surface 29 is mountedbeneath the diagonally oriented wires to reflect a controlled level ofheat to the support material during fusing. The wires support thesupport material with a minimum of contact during fusing to prevent heatconduction therebetween and thereby thermally isolate the supportmaterial from the platen to produce a higher degree of control of thetemperature for selective fusing by reducing uneven heat conduction asproduced by a flat platen surface. Further, the provision of a minimumcontact platen 18 in the present invention does not pre-heat the supportmaterial when initially conveyed into the fusing area since theplurality of wires do not retain heat as a flat surface does. The wiresare diagonally oriented to prevent the wires from contacting aparticular area of the support material as the sheet passes under thefusing lamp. Therefore, it should be apparent that the present inventionprovides a more controlled temperature environment for effectingselective fusing of a toner image to a sheet of support material ascompared to prior art devices.

In the above description there has been disclosed an improved method andapparatus for selectively fusing a toner image to a support material tothe exclusion of toner adhering to the background areas thereof. Thesurface to be developed was described for convenience of illustration asbeing that of a xerographic drum, but the invention may be used to fusetoner images produced on other well-known photosensitive members in theform of plates, belts, webs or coated papers.

' Further, it is within the scope of the present invention to bond tonerimages to other forms of support material than sheets as disclosedherein, such as, for example, webs and the like.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its essential teachings.

What is claimed is:

l. A method for selectively fusing developer material supported in imageconfiguration on a support medium to effect a permanent bondtherebetween to the exclusion of fusing randomly deposited developermaterial supported in non-image areas of the support medium comprisingthe steps of applying a predetermined level of heat to a support mediumbearing developer material in image configuration and randomly depositeddeveloper materials in non-image configuration to fuse the developermaterial in image configuration to the exclusion of developer materiallying in non-image areas and thermally isolating the support medium fromheat conduction during application of said predetermined level of heatby supporting the support medium with a low heat retaining platen whilethe toner is being heated, said platen contacting the support mediumover a small area to effectively eliminate heat transfer between platenand support medium. 2. A method for selectively fusing developermaterial supported in image configuration on a support medium to effecta permanent bond therebetween to the exclusion of fusing randomlydeposited developer material supported in non-image areas of the supportmedium comprising the steps of applying a predetermined level of heat toa support medium bearing developer material in image configuration andrandomly deposited developer materials in non-image configuration tofuse developer material in image configuration to the exclusion ofdeveloper material lying in non-image areas,

and supporting the support medium with a grid platen to eliminate heatconduction from the support medium during fusing.

3. Apparatus for fusing toner to a support medium comprisa source ofheat energy for heating toner to bond the toner to a support medium and,

a low heat retaining platen for supporting the support medium whiletoner is being heated, said platen contacting a support medium over asmall area to effectively eliminate heat transfer between platen andsupport medium for thermally isolating a support medium from the platen.

4. The apparatus of claim 3 wherein said source of heat energy includesmeans for generating heat of a level to bond toner in predeterminedquantities to the support medium while leaving toner in less quantitiesunbonded to the support medium.

5. The apparatus of claim 3 wherein said source of heat energy includesmeans for generating radiant heat energy.

6. The apparatus of claim 5 further including a reflective surfaceadapted to reflect heat through the platen to the support medium.

7. The apparatus of claim 3 wherein said source of heat energy includesan infrared lamp.

8. The apparatus of claim 3 further including removal means for removingunbonded toner from a support medium.

9. The apparatus of claim 3 wherein the platen comprises a plurality ofelongated wire members.

10. The apparatus of claim 9 wherein the plurality of elongated wiremembers are diagonally oriented.

11. The apparatus of claim 3 including edge contact means to maintainthe support medium in a flat condition during fusing.

1. A method for selectively fusing developer material supported in imageconfiguration on a support medium to effect a permanent bondtherebetween to the exclusion of fusing randomly deposited developermaterial supported in non-image areas of the support medium comprisingthe steps of applying a predetermined level of heat to a support mediumbearing developer material in image configuration and randomly depositeddeveloper materials in non-image configuration to fuse the developermaterial in image configuration to the exclusion of developer materiallying in non-image areas and thermally isolating the support medium fromheat conduction during application of said predetermined level of heatby supporting the support medium with a low heat retaining platen whilethe toner is being heated, said platen contacting the support mediumover a small area to effectively eliminate heat transfer between platenand support medium.
 2. A method for selectively fusing developermaterial supported in image configuration on a support medium to effecta permanent bond therebetween to the exclusion of fusing randomlydeposited developer material supported in non-image areas of the supportmedium comprising the steps of applying a predetermined level of heat toa support medium bearing developer material in image configuration andrandomly deposited developer materials in non-image configuration tofuse developer material in image configuration to the exclusion ofdeveloper material lying in non-image areas, and supporting the supportmedium with a grid platen to eliminate heat conduction from the supportmedium during fusing.
 3. Apparatus for fusing toner to a support mediumcomprising a source of heat energy for heating toner to bond the tonerto a support medium and, a low heat retaining platen for supporting thesupport medium while toner is being heated, said platen contacting asupport medium over a small area to effectively eliminate heat transferbetween platen and support medium for thermally isolating a supportmedium from the platen.
 4. The apparatus of claim 3 wherein said sourceof heat energy includes means for generating heat of a level to bondtoner in predetermined quantities to the support medium while leavingtoner in less quantities unbonded to the support medium.
 5. Theapparatus of claim 3 wherein said source of heat energy includes meansfor generating radiant heat energy.
 6. The apparatus of claim 5 furtherincluding a reflective surface adapted to reflect heat through theplaten to the support medium.
 7. The apparatus of claim 3 wherein saidsource of heat energy includes an infrared lamp.
 8. The apparatus ofclaim 3 further including removal means for removing unbonded toner froma support medium.
 9. The apparatus of claim 3 wherein the platencomprises a plurality of elongated wire members.
 10. The apparatus ofclaim 9 wherein the plurality of elongated wire members are diagonallyoriented.
 11. The apparatus of claim 3 including edge contact means tomaintain the support medium in a flat condition during fusing.